Bubble Bobble Evolution is a game in the Bubble Bobble series for the PSP system. Bub and Bob, the two main characters in the series, have been trapped in costumed versions of their bubble dragon forms (instead of physically into bubble dragons) and are separated into each of the two Towers of Entertainment. Bub and Bob must traverse the towers while defeating the various enemies inside it. The game's levels are now in a cylindrical structure, and there are puzzles that must be completed to progress through the game, such as activating switches and moving items.